DE102015122200B4 - Quiescent current brake with improved counter-friction surface due to laser processing of the same - Google Patents

Abstract

Electromagnetically released closed-circuit brake with a coil carrier with magnet coil and compression springs arranged in the coil carrier and distributed over the circumference of the coil carrier, with:- a brake rotor with one or more friction surfaces,- an armature disk with one or more metallic counter-friction surfaces, characterized in that one or several counter-friction surface(s) are provided with a surface roughness in the form of indentations and elevations arranged at the edges of the indentations, at least in one friction area (B), by these indentations and elevations being produced by the action of a laser beam in the friction area (B), and that these Areas on the counter friction surface(s) with a surface roughness in the friction area (B) are separated from one another at regular or irregular intervals, the surface roughness generated on the counter friction surface(s) being in the range between Ra= 1.6 µm to Ra= 4.0 µm and that the counter friction surface(s) is/are hardened after laser processing by surface hardening processes such as gas nitriding, plasma nitriding, gas nitrocarburizing or plasma nitrocarburizing.

Description

The present invention relates to the production of quiescent current brakes, in which modifications of the surface roughness and the surface structure of the mechanical counter-friction surface(s) are produced by means of a laser, namely according to the preamble of the main claim. In the following, these modifications are referred to as surface roughness. These improvements in the counter-friction surfaces, in particular on quiescent current brakes such as electromagnetically releasing spring-loaded brakes, can also be used in fluid-actuated disc brakes or permanent magnet brakes.

Quiescent current brakes are generally understood to mean braking systems which unfold their braking effect without an external supply of energy, ie for example in the de-energized state or in a state without the supply of external pressure medium.

Modern electric drives are often designed as controllable drives. In normal operation, these take over the complete movement profile of a system. This ranges from acceleration to braking. In normal operation, brakes integrated into the drive train only perform a holding function. The system is only braked to a standstill with the help of the brakes as part of a dynamic braking process in emergency situations, in the event of a power failure or in the event of uncontrolled movements. During such a braking process, friction work is performed.

The brakes described above are usually equipped with organically bound friction linings on brake rotors, which are in contact with metallic counter friction surfaces. Such conventional brake systems only reach their full torque after a bedding-in process. This is often also referred to as the running-in process or conditioning. The conditioned and thus optimized state of the brake is only achieved or maintained after regular friction work has been carried out.

When using the controlled drives described, however, no friction work is performed in normal operation. For reasons of cost, the system manufacturer often does without a grinding-in process for the brake system as part of the commissioning of a system. Braking processes as a result of emergency situations or power failures are also very rare, so that a conditioned state of the brakes is not maintained.
It follows from this that conventional braking systems do not reach their full torque.

If an adapted abrasive surface roughness is provided in the friction area on the side of the metallic counter friction surface, a grinding-in process and maintaining the conditioned state can be dispensed with. The adapted surfaces lead to a wedging of the friction partners, the friction lining and the counter friction surface, close to the surface, and thus to an increased coefficient of friction. As a result of the increased coefficient of friction, the torque that can be transmitted is greater.

Numerous modifications, processing and coating methods of metal counter-friction surfaces are known from the prior art. So will in the DE 10 2007 037 612 A1 proposed to embed abrasive hard material grains in a carrier mass on the friction surface. Although this leads to an increased coefficient of friction, it means a great deal of processing work and expense.

In the DE 10 2004 049 559 A1 Grooves or groove structures are proposed on counter friction surfaces in the circumferential direction, with the counter friction surface containing the groove pattern and the friction lining being provided with corresponding springs. This leads to a great deal of processing effort on the two friction partners that have to be adapted to one another. In addition, grooves and grooves in the circumferential direction lead to an insignificant increase in the coefficient of friction. Recesses are provided in the radial direction, but these do not contribute to increasing the roughness but only serve to remove the abrasion material that is produced.

Also, for example, in the DE 10 2006 017 207 A1 and the DE 195 24 144 A1 suggested enlarging the surface of brake discs by circumferential grooves or recesses for better heat dissipation. Although this surface structure leads to increased surface roughness in the radial direction, there is no abrasive effect in the circumferential direction (rubbing direction). An increase in the coefficient of friction is therefore not to be expected.

In the DE 10 2005 062 522 A1 discloses a method for the non-positive connection of the end faces of two machine components that are always immovable relative to one another, for the transmission of high torques or transverse forces. For this purpose, the surface of a first machine component is machined by means of a focused laser beam and protrusions are applied to this surface which are harder than the material on the surface of another machine component to which the former is to be connected. However, this publication does not deal with brakes in any form, since the parts are connected to each other in a force-fitting manner, which also during remain stationary relative to each other during operation, so that in particular the operation of a brake in which a friction surface and its associated counter-friction surface are movable relative to each other is not considered by the document.

In the DE 10 2006 036 151 A1 a method for the surface treatment of a workpiece with a tribologically stressable surface is disclosed. A laser with a particularly short pulse duration and thus a low energy transfer is used here. This publication discloses the formation of pockets by means of laser processing and ultra-short pulses with a pulse duration of less than 100 ps are used. This publication leads away from the essence of the invention described here because, due to the use of ultra-short laser pulses, burrs or elevations cannot arise on the surface of the workpiece to be machined.

the DE 696 20 972 T2 discloses friction plates (1,2,3,4,5,6) for a friction clutch for providing a function of braking, holding, accelerating or decelerating by depressing and contacting one friction element against the other friction element of the friction clutch, the friction clutch consisting of two friction plates , one of which is made of metals, non-metallic materials or inorganic materials. One friction plate has a friction portion that is selectively pressed against the other friction plate and another non-contacting portion. The friction portion is formed as a plurality of projections (1a, 2a, 3a, 4a, 5a, 6a) formed by cutting away, engraving a plurality of grooves, cutting away non-contacting portions, or forming a plurality of projections in a form-fitting manner on the surface generate the friction section. The area ratio of the friction portion to the total area of the friction plate, namely the total of the contact portion plus the non-contact portion, is less than 60%, preferably less than 10%, thereby varying the generated frictional force and maintaining stable frictional performance.

WO2013/060 313 A1 discloses a method for processing a metallic friction surface for wet-running applications. The invention is characterized in that the metal friction surface is machined with a laser.

The object of the present invention is therefore to specify a significant improvement in the achievable coefficients of friction for a quiescent current brake or a comparable brake, specifically for a quiescent current brake that has a brake rotor with friction linings made of an organically bound material and at least one armature disk interacting therewith and possibly also a Flange plate with counter friction surface(s). The counter friction surface(s) (GF) have a friction area (B) in which, according to the invention, an abrasive surface roughness is produced using a laser beam. The shape of the friction surface(s) of the metal counter-friction surface(s) can be circular, oval, square or rectangular. The effect of the laser beam creates indentations on and/or the counter-friction surface(s) (GF) of the metal anchor plate and/or the flange plate, with elevations/burrs being produced at the edges of the indentations at the same time. The indentations and elevations/burrs create an increased surface roughness of the counter friction surface(s) (GF) acting in the direction of friction, which results in a higher coefficient of friction for the power-off brake. The increase in the coefficient of friction is independent of the organically bonded friction lining on the brake rotor. The improvement according to the invention also leads to a cost-effective method for producing abrasive surface roughness on the counter-friction surface(s) (GF) of a power-off brake or a comparable brake. Furthermore, the improvement according to the invention makes it possible to produce a large number of fail-safe brakes with reproducible abrasive surface roughness using a user-friendly and simple method, ie a time-efficient method.

The object formulated above is achieved according to the invention by product claim 1 and method claim 14 .

The generation of the abrasive surface roughness in the friction area (B) of the counter-friction surface(s) (GF) of the armature disk and, if necessary, the flange plate of a closed-circuit brake is produced using a laser, for example a neodymium-doped yttrium aluminum garnet laser or a comparable laser. To solve the technical problem, the laser parameters to be determined are the mean power of the laser, the position of the focus of the laser beam, the pulse frequency of the laser, the marking speed of the laser and the number of repetitions of the laser processing on the counter friction surface(s). Here, the form, shape and extent of the counter-friction surface(s) together with the areas to be machined on the aforementioned workpiece are defined using a computer-aided design program, for example a CAD program, and specified to the laser. The area(s) of the counter-friction surface(s) that have an abrasive surface roughness in the friction area (B) can be here be arranged at regular or irregular distances from one another and be designed in the form of circle segments, square or rectangular segments. The surface area (BR) with abrasive surface roughness that can be occupied by the friction area (B) on the metal friction surface is in the range of 10% - 80% of the metal friction surface. The material of the counter friction surface (GF) to be machined can either be C45, C15E, DC01, S235JR, S355J263, X6Cr17 or a comparable material.

During the laser processing of the workpiece, radial lines (transverse to the rubbing direction) directed outwards can be formed. The lines formed can also be formed at any other angles. Alternatively, zigzag lines, oval, circular lines or cross patterns formed from lines with an angle S of between 5 and 90 degrees to one another can also be formed. Furthermore, the surface roughness can also be carried out in the form of inscriptions. After all the necessary parameters and information have been passed on to the laser, when it is applied to the workpiece, the material of the metal disc to be machined is vaporized or ionized in the center of the laser beam due to the high energy density of the laser beam, and thus depressions are formed in the surface of the Workpiece or the counter friction surface (s) generated. The elevations/burrs on the edges of the depressions are fed from the melt of the laser track, so that material removal takes place on average when the metal counter-friction surface(s) are machined. The creation of burrs/elevations results in a sharp-edged, irregular profile of the counter-friction surface(s), which results in the interaction of the counter-friction surface(s) (GF) with the brake rotor and its friction surface(s) with organic lining, causing the interacting surfaces to grip .

The laser creates an abrasive surface roughness with elevations and depressions in the areas defined (by the computer-aided design program) in the counter friction surface(s), with roughness values in the range of R _a = 1.6 µm to R = 4.0 µm being achieved. Here, R _a corresponds to the arithmetic mean. This represents the arithmetic mean of the absolute values of the profile deviations within the reference section. The R _a value is determined by means of a tactile roughness measurement, ie by the so-called touch step method. In this case, a probe tip is drawn over the surface and the R _a value is calculated from the sensory information obtained.

According to the invention, the information and parameters transferred to the laser in order to obtain the above-mentioned range of roughness values of the workpiece are in the range of 90-100 W for the mean power of the laser, in the range of 20-200 kHz for the pulse frequency of the laser, and for the marking speed of the laser in the range from 100 to 300 mm/s. The number of repetitions of the laser work steps when creating the abrasive surface roughness on the counter friction surface(s) is one, i.e. the depressions and elevations created on the counter friction surface are only swept over by the laser once during processing of the workpiece. When creating an abrasive surface roughness, the focus of the laser beam can be directly on the friction surface of the counter-friction surface(s) - or in a range of 0.1 mm - 2.5 mm in or below the counter-friction surface(s). In this case, a defocused and therefore wider laser beam hits the counter friction surface(s), resulting in wider indentations on the surface of the friction surface.

In the method described, it should be noted that with other parameter ranges used, surface structures with roughness values of up to R=50 μm can also be achieved, although this is not desirable in the present application of the invention, since in the case of such high roughness values R _a the resulting wear is too high when braking on a fail-safe brake.

With workpieces that change in height, the focus of the laser beam is tracked according to the change in height of the workpiece, so that the focus setting is constant when processing a workpiece for different heights of the workpiece. Following the laser processing, surface hardening processes such as gas nitriding, plasma nitriding, gas nitrocarburizing or plasma nitrocarburizing or a comparable process can be used according to the invention. The achievable hardening depths of these processes are approx. 0.5 mm to 1.0 mm, significantly deeper than with the previously used laser process. In addition to the methods mentioned above, laser hardening methods or surface layer hardening methods can also be used. Due to the hardening process carried out, roughness peaks and also deeper line structures can be made more wear-resistant after the laser process.

Workpieces to be machined, for example metallic counter-friction surface(s) of the quiescent current brakes in question, are often coated with materials for corrosion and/or transport protection in order to be protected from environmental influences during longer storage times. examples of such Coatings can be any type of organic or inorganic coating, for example also phosphate coatings, lacquer layers, metal layers or other comparable coatings. In preparation for further processing, for example with the process presented above for generating an abrasive surface roughness on counter friction surface(s), the aim is to remove the aforementioned coatings made of organic or inorganic materials as completely as possible in order to obtain a metallic surface of the workpiece that is as clean as possible . Coatings made of organic or inorganic materials can also be removed using a laser in addition to known methods from the prior art. The laser works in a mode in which the surface of the workpiece is completely covered by the laser beam during processing and is swept over either once or several times. Here, the laser is operated as edge-to-edge as possible and with little overlapping. The shape and size of the area to be removed is determined using a computer-aided design program, for example a CAD program or a comparable program, and can consist of contiguous or separate areas on the surface of the workpiece. A diode-pumped fiber laser can be used as the laser, for example a neodymium-doped yttrium aluminum garnet laser. In this case, circular segments or a square or rectangular shape of the areas on the surface of the workpiece from which a coating is removed are possible.

A crucial parameter for the speed of removing coatings from the surface of a workpiece is the height of the workpiece to be machined. This is decisive for the position of the focus of the laser beam in relation to the workpiece to be processed and is transferred to the laser as a parameter. A value between 0.1 mm and 2.5 mm is subtracted from the actual height of the workpiece so that the focus of the laser beam is within the workpiece. Due to the defocusing that occurs as a result, a wider laser beam acts on the surface of the workpiece, which leads to faster removal of the coating of the organic or inorganic material of the workpiece. The parameters of the laser beam are a marking speed of 1900 - 2000 mm/s in connection with a pulse frequency in the range of 190-200 kHz and an average power of the laser in the range of 60 - 80 W. The advantage of this choice of parameters is an optimized working speed , so that as many workpieces as possible can be processed in a given time. The processing of the laser beam and the removal of organic and inorganic coatings creates holes without burrs when the laser interacts with the workpiece. The profile of these processed areas can be determined using a tactile measurement, for example a measuring needle that runs over the surface. It should be noted here that there are almost no elevations at the holes, so that increased roughness can be measured by means of a tactile measurement, but this does not lead to an increased coefficient of friction and thus to an increased torque transmission with a closed-circuit brake due to the lack of elevations.

The areas that are to be given an abrasive surface roughness overlap, at least in part, with an optionally preceding removal of a coating made of organic and inorganic material in previously defined areas of the workpiece. When the areas are covered, this results in the technical advantage of a surface that is almost completely free of organic and inorganic materials for further processing. Said removal of coatings made of organic or inorganic material can also be achieved by other known cleaning methods from the prior art.

It is also planned not to provide the entire friction area (B) with the abrasive surface roughness, so that in the areas in the circumferential direction, i.e. between the areas of abrasive surface roughness, the abrasion material can be removed from the friction gap by means of a smooth surface of the workpiece.

It is particularly advantageous for maintaining the abrasive surface roughness in the case of a dynamic braking process to harden the surface of the metal friction partner using a surface layer hardening process such as induction hardening, and thus to minimize wear on the side of the metal friction partner.

If the metallic counter friction partner is covered with an organic or inorganic coating after the abrasive surface roughness has been produced, the counter friction partner can be additionally protected against corrosion. For example, chemically deposited phosphate layers or galvanically deposited metallic layers made of zinc, nickel or zinc-nickel can be used here. A ceramic coating is also possible.

The advantage of the invention over the prior art is that the movable counter-friction surface(s) of a power-off brake can be increased with an abrasive surface roughness of the coefficient of friction can be introduced very inexpensively and independently of the friction lining using the methods mentioned. An adjustment of the geometry of the friction lining is not necessary. Another advantage is that the abrasive surface roughness can be produced reproducibly. In addition, the area of abrasive surface roughness can be protected from premature wear by a surface hardening process. A further advantage of the invention is the independence from cutting processes, since when workpieces are machined with cutting tools, wear occurs on the latter, which cannot be observed when using a laser tool.

The object of the invention is achieved with the features of the main claim and the secondary claims. Further advantageous details of the invention result from the dependent claims and from the description of the drawings mentioned below.

• 1 eine Schnittdarstellung einer elektromagnetisch lüftenden Federdruckbremse in Ruhestrombauweise;
• 1.1 einen metallischen Gegenreibpartner der Bremse aus 1 in runder Bauform;
• 2 eine elektromagnetisch lüftende Federdruckbremse rechteckiger Bauform;
• 2.1 einen metallischen Gegenreibpartner der Bremse aus 2 in rechteckiger Bauform;
• 3 eine Schnittdarstellung einer hydraulisch lüftenden Federdruckbremse als Scheibenbremse;
• 3.1 eine Bremsscheibe der Scheibenbremse aus 3;
• 4 einen metallischen Gegenreibpartner der Federdruckbremse aus 1 mit abrasiver Oberflächenrauigkeit im markierten Bereich;
• 5 eine exemplarische schematische Darstellung einer Oberflächenstruktur analog zu 4 mit radial verlaufender Struktur;
• 6 eine exemplarische schematische Darstellung einer Oberflächenstruktur analog zu 5 mit kreuzförmig verlaufender Struktur;
• 7 eine durch das genanntes Laserverfahren erzeugte Rauigkeit auf der Oberfläche eines zu bearbeitenden Werkstücks in Form von zwei radial nach außen laufenden Linien, wobei diese Linien durch Vertiefungen und an den Rändern der Vertiefungen befindlichen Erhebungen/Grate definiert werden;
• 8. ein zwei-dimensionales Profil der abrasiven Oberflächenrauigkeit auf einer Gegenreibfläche (GF) von 7, wobei die Oberflächenrauigkeit mittels der Bearbeitung durch einen Laser erzeugt wird.
• 9: Vergleichsmessungen von Ruhestrombremsen mit laserstrukturierten Gegenreibflächen im Vergleich mit Ruhestrombremsen mit gefrästen Gegenreibflächen.

show:

• 1 a sectional view of an electromagnetically releasing spring-loaded brake in quiescent current design;
• 1 .1 a metallic counter friction partner of the brake 1 in round design;
• 2 an electromagnetically releasing spring-loaded brake of rectangular design;
• 2 .1 a metallic counter friction partner of the brake 2 in rectangular design;
• 3 a sectional view of a hydraulically releasing spring-loaded brake as a disc brake;
• 3 .1 a brake disc of the disc brake 3 ;
• 4 a metallic counter-friction partner of the spring-loaded brake 1 with abrasive surface roughness in the marked area;
• 5 an exemplary schematic representation of a surface structure analogous to 4 with radial structure;
• 6 an exemplary schematic representation of a surface structure analogous to 5 with cross-shaped structure;
• 7 a roughness produced by said laser process on the surface of a workpiece to be machined in the form of two radially outwardly extending lines, these lines being defined by indentations and elevations/ridges located at the edges of the indentations;
• 8th . a two-dimensional profile of the abrasive surface roughness on a counter friction surface (GF) of 7 , wherein the surface roughness is produced by means of laser processing.
• 9 : Comparative measurements of power-off brakes with laser-structured counter-friction surfaces in comparison with power-off brakes with milled counter-friction surfaces.

1 shows a full section of an electromagnetically releasing spring-loaded brake (FDB) in closed-circuit design, in which metallic counter-friction partners (G) such as the armature disk (1) and the flange plate (2) are used, which form the metallic counter-friction surfaces (GF). According to the invention, these counter-friction surfaces (GF) are formed by means of a laser with an abrasive surface roughness/surface structure in the respective friction area of the counter-friction surface.

The coil carrier (3), which contains the compression springs (4) and the magnetic coil (5), is permanently attached to the motor end shield (M). The armature disk (1) is guided in a torque-proof manner via bushings (6) and can move axially along the axis of rotation (A). The rotor (7), which consists of a friction lining carrier (9) connected to organic friction linings (8) on both sides, is non-rotatably connected to the shaft (11) via a hub (10) and can rotate about the axis of rotation (A) and move axially move parallel to the axis of rotation. The flange plate (2) is firmly clamped between the motor end shield (M) and the coil carrier (3).

The braking effect of the spring-loaded brake (FDB) is generated by clamping the rotor (7) between the armature disk (1) and the flange plate (2). The axial force required for this is applied by the pressure springs (4). Thus, the shaft (11) is held and prevented from rotating about the axis of rotation (A) via the rotor (7), which is non-rotatably connected to the shaft (11) via the hub (10).

To open the spring-loaded brake (FDB), the solenoid (5) is connected to an electrical power source. The resulting magnetic field pulls the armature disk (1) against the force of the compression springs (4) in the direction of the coil carrier (3), so that the rotor (7) is released and the braking effect is canceled. The shaft (11) is thus freely rotatable again.

1 .1 shows a metallic counter-friction partner (G) of round design, here an example of an armature disk (1) as found in the spring-loaded brake (FDB). 1 is used. The highlighted area (B) marks the counter friction surface (GF) on which the organic friction lining (8) of the Rotor (7) with the metallic counter friction partner (G) comes into contact when a corresponding brake is closed. The design shown as an example is used in almost all industrial sectors. The flange plate (2) off 1 has a same area (B) as a counter-friction surface (GF) which comes into contact with the second organic friction lining (8) of the same rotor (7).

2 shows a spring-loaded brake (FDB) with a closed-circuit current design and a rectangular design, as used in elevator technology, for example. The functional principle corresponds to that in 1 described spring-loaded brake. However, here two brake circuits act on one rotor (7). For a better overview, in 2 only one brake circuit consisting of coil carrier (3) and armature disk (1) and the rotor (7) with the annular friction lining (8) is shown.

2 .1 shows a metallic counter-friction partner (G) in a rectangular design, here a rectangular armature disk (1) as in 2 shown. The highlighted area (B) marks the counter-friction surface (GF) on which the organic friction lining (8) of the rotor (7) comes into contact with the metallic counter-friction partner (G) when a corresponding brake is closed. The design shown is primarily used in the area of passenger and freight elevators. The flange plate (2) shown here 2 again has a similar area (B) as a counter-friction surface (GF) which comes into contact with the second organic friction lining (8) of the same rotor (7).

3 shows a full section of a hydraulically releasing spring-loaded brake (FDB), shown here as a disc brake. The brake disc (12) with the metal counter-friction surfaces (GF) forms the metal counter-friction partner (G). The cylinders (13) are stationarily arranged and rigidly connected to one another via the bracket (16). The pistons (14) are moved in the direction of the brake disc (12) by the axial force of the compression springs (4), which are supported on the cylinder cover (15). The brake disc is clamped via the friction lining carrier (9), which is firmly connected to the piston (14) with the friction lining (8), and the braking effect is thus generated. To open the spring-loaded brake (FDB), pressure medium such as hydraulic oil or compressed air is supplied via the pressure medium supply (17), which moves the pistons (14) against the spring force of the compression springs (4) in the direction of the cylinder cover (15). The resulting excess pressure in the area of the pressure springs (4) can escape through the vent holes (18). This movement of the pistons (14) releases the brake disc (12).

3 .1 shows a metal brake disc (12), which serves as a metal counter-friction partner (G). The highlighted area (B) marks the counter-friction surface (GF) on which the organic friction lining (8) comes into contact with the metallic counter-friction partner (G) when a corresponding brake is closed. The design shown is mainly used in the area of passenger and freight elevators, but also in general mechanical engineering.

4 shows a metallic counter-friction partner (G), here an armature disk (1), analogous to 1 .1, which (r) in the area (B), in which the friction lining (8) and the counter friction partner (G) touch, is not provided with an abrasive surface roughness over the entire surface, but only partially. These areas (BR) can be provided with multiple interruptions (U) and can be located at regular or irregular distances from one another in the circumferential direction.

5 shows a representation of an abrasive surface roughness in the shape of a segment of a circle made up of grooves which are formed in the radial direction, ie transversely to the rubbing direction.

6 shows a representation of an abrasive surface roughness, which is formed by grooves arranged as a cross pattern. In the example shown, the grooves arranged in the cross pattern intersect at a cutting angle (S) of 90°, with angles in a range between 10° and 90° also being possible.

7 shows a picture taken with the help of an optical microscope and enlarged by a factor of 500 of a part of the abrasive surface roughness on the surface of a counter-friction surface (GF) of a metallic disc such as an armature disc or flange plate, in the form of radially outwards (transverse to the friction direction) running grooves. It should be noted here that the indentations produced by means of the laser have elevations at the edge of these indentations, which contribute to increasing the surface roughness. The surface roughness is in a range from R _a = 1.6 µm to R = 4 µm.

8th shows an elevation profile of the in 7 recorded surface structure of a workpiece which has been processed using a laser. Here, the elevations are clearly visible, which are located directly on the depressions. Using this method, roughness values in the range of R=1-50 μm can be achieved, with values in the range of R _a =1.6 μm to R _a =4.0 μm being preferred, since these contribute to an increased coefficient of friction and to acceptable wear in the operation of a closed-circuit brake.

9 shows the results of static coefficient of friction measurements of quiescent current brakes, with the hatched bar representing the coefficient of friction of counter-friction surface(s) with a laser-machined surface and the gray bar representing the coefficient of friction of counter-friction surface(s) with milled surfaces. The torques that can be transmitted through the machined surfaces are measured in a test stand and the coefficients of friction for the various machined surfaces are determined from this. This results in the result that the transmissible torques with laser-machined counter-friction surfaces of metallic discs in quiescent current brakes are 20% - 35% higher compared to milled counter-friction surface(s) of metallic discs in quiescent current brakes, which means that the technical advantage of the presented teaching according to the invention is shown.

Reference List

FDB

spring pressure brake

G

metallic counter friction partner

GF

metallic counter friction surface

A

axis of rotation

M

motor bearing shield

B

Contact surface between counter friction partner and friction lining

BR

Area of abrasive surface roughness or abrasive surface structure

HE

bumps/ridges

VT

indentations

u

Interruption between areas BR

S

cutting angle

1

armature disk

2

flange plate

3

coil carrier

4

compression spring

5

magnetic coil

6

Rifle

7

rotor

8th

friction lining

9

friction lining carrier

10

hub

11

Wave

12

brake disc

13

cylinder

14

Pistons

15

cylinder cover

16

hanger

17

pressure medium supply

18

vent hole

Claims (23)

Electromagnetically released closed-circuit brake with a coil carrier with magnet coil and compression springs arranged in the coil carrier and distributed over the circumference of the coil carrier, with: - a brake rotor with one or more friction surfaces, - an armature disk with one or more metallic counter-friction surfaces, characterized in that one or several counter-friction surface(s) are provided with a surface roughness in the form of indentations and elevations arranged at the edges of the indentations, at least in one friction area (B), by these indentations and elevations being produced by the action of a laser beam in the friction area (B), and that these Areas on the counter friction surface(s) with a surface roughness in the friction area (B) are separated from one another at regular or irregular intervals, the generated surface roughness on the counter friction surface(s) being in the range between R _a = 1.6 µm to R _a = 4.0 µm and that the counter After laser processing, the friction surface(s) is/are hardened by surface hardening processes such as gas nitriding, plasma nitriding, gas nitrocarburizing or plasma nitrocarburizing. Quiescent current brake after claim 1 , characterized in that the counter-friction surface(s) have a circular, oval, square or rectangular shape. Quiescent current brake after claim 2 , characterized in that the counter friction surface(s) consist of an iron or cast material such as C45, C15E, DC01, S235JR, S355J2G3 or X6Cr17. Quiescent current brake after claim 2 , characterized in that the counter-friction surface(s) in the friction area (B) have one or more areas with a surface roughness in the form of circular segments, square or rectangular segments. Quiescent current brake after claim 3 characterized in that the areas with surface roughness in the friction area (B) occupy a surface area of 10% - 80% of the counter friction surface(s). Quiescent current brake according to one of the preceding claims, characterized in that indentations and elevations are formed on the counter-friction surface(s) essentially in radial lines (transverse to the direction of friction). Quiescent-current brake according to one of the preceding claims, characterized in that depressions and elevations on the counter-friction surface(s) are formed in a zigzag shape or in the form of inscriptions. Quiescent current brake according to one of the preceding claims, characterized in that depressions and elevations on the counter-friction surface(s) are formed in an oval or circular shape. Quiescent current brake according to one of the preceding claims, characterized in that indentations and elevations on the counter-friction surface(s) are designed as a cross pattern with a cutting angle S, the cutting angle having a value between 10 and 90 angular degrees. Quiescent current brake according to one of Claims 1 - 9 , characterized in that the counter-friction surface(s) is/are hardened by a laser hardening process such as induction hardening after the laser processing. Quiescent current brake according to one of Claims 1 - 10 characterized in that the counter-friction surface(s) is/are covered with an organic or inorganic coating for corrosion and/or transport protection after the laser processing. Quiescent current brake according to one of the preceding claims, furthermore with a flange plate with one or more metallic counter-friction surface(s) Use of a counter friction surface claim 1 - 12 for a fluid-actuated brake or a permanent magnet brake. Method for machining the counter-friction surface(s) of an electromagnetically released fail-safe brake with a coil carrier with a magnet coil and compression springs arranged in the coil carrier and distributed over the circumference of the coil carrier, with: - a brake rotor with one or more friction surfaces, - an armature disk with one or more metal ones Counter-friction surfaces, the counter-friction surface(s) being provided in a friction area (B) with a surface roughness in the form of indentations and elevations arranged on the edges of the indentations, in that these indentations and elevations are produced by the action of a laser beam in the friction area (B), and that the areas on the counter friction surface(s) with a surface roughness in the friction area (B) are separated from one another at regular or irregular intervals, the generated surface roughness on the counter friction surface(s) being in the range between R _a = 1.6 µm to R _a = 4.0 µm, thereby marked records that the laser is a diode-pumped fiber laser, and when creating the surface roughness, the average power of the laser is in the range of 90-100 W, the pulse frequency of the laser is in the range of 20-200 kHz, and the marking speed of the laser is in the range of 100 up to 300 mm/sec. procedure after Claim 14 , characterized in that the laser is a neodymium-doped yttrium aluminum garnet laser. procedure after Claim 14 , characterized in that the areas of surface roughness that are produced by the laser on the counter friction surface(s) are defined by means of a computer-aided design program. procedure after Claim 14 , characterized in that the focus of the laser beam is on the surface of the counter friction surface(s). procedure after Claim 14 , characterized in that the focus of the laser beam is in the range of 0.1 mm to 2.5 mm in the counter friction surface or surfaces. procedure after Claim 14 , characterized in that organic or inorganic coatings on the counter-friction surface(s) are at least partially removed before surface roughness is produced by a defocused laser beam processing the counter-friction surface(s). procedure after claim 19 , characterized in that the area or areas on the counter-friction surface(s) where coatings are removed are defined by means of a computer-aided design program. procedure after claim 19 , characterized in that the focus of the laser beam is in the range of 0.1 mm to 2.5 mm within the surface of the metallic workpiece. procedure after claim 19 , characterized in that the laser is a diode is a pumped fiber laser where, when removing coatings, the average power of the laser is in the range of 60-80 W, the pulse frequency of the laser is in the range of 190-200 kHz and the marking speed of the laser is in the range of 1800-2000 mm/sec. procedure after claim 19 , characterized in that the laser is neodymium-doped yttrium aluminum garnet laser.

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